Aerobic exercise is all about getting into the right heart-rate zone. Heart rate refers to beats per minute, and it's used to measure exercise intensity. More than one formula can help you reach your heart rate goals, and the "best" one depends on how accurate you want it to be and how good you are at math. If you're new to exercise, see your doctor before starting a new routine.
Maximum Heart Rate
The quest for your optimal cardio zone starts with figuring out your maximum heart rate. For a quick estimate, subtract your age from the number 220: So at 25 years old, your maximum heart rate is 195 beats per minute, or 220 minus 25. If you don't mind some extra number crunching, the American College of Sports Medicine recommends multiplying your age times 0.67, then subtracting the result from 206.9 for a rate that is more accurate for all age groups. At age 25, your maximum heart rate is about 190 with this formula. To take your pulse, place two fingers on either the carotid pulse site on your neck or the radial pulse site on your wrist. Count your pulse for 10 seconds, then multiply the number times six to find your beats per minute. The American Council on Exercise recommends against putting too much pressure on your carotid as it could slow your pulse rate.
For moderate cardio, aim for 50 to 70 percent of your maximum heart rate. So at age 25, your goal is between 97.5 and 136.5 bpm. Exercises likely to get you there include walking briskly, dancing freestyle, pushing a heavy lawn mower or cycling on flat ground. If you go the moderate cardio route, the Centers for Disease Control and Prevention recommend at least 150 minutes of exercise per week but note that 300 weekly minutes is even better.
If you long for a challenge, use your heart rate to aim for a vigorous cardio workout. You'll know you're in the zone when you reach 70 to 85 percent of maximum, or 136.5 to 165.75 bpm for that 25-year-old. Jogging, swimming laps, taking an aerobic dance class and cycling on hilly ground all offer vigorous cardio exercise. You can get away with shorter workouts with vigorous cardio compared to moderate cardio; the CDC recommends at least 75 minutes per week and considers 150 minutes per week ideal.
The Karvonen Formula
The Karvonen formula for calculating target heart rate allows more customization but requires extra planning. Check your pulse before rising in the morning to find your resting heart rate, or RHR, then subtract this number from your maximum heart rate to find your heart rate reserve, or HRR. So if your maximum heart rate is 190 bpm, and your resting heart rate is 70 bpm, your HRR is 120 bpm. Multiply your HRR times 70 percent, then multiply your HRR times 85 percent and add your RHR to both products to find your target heart-rate range. In the example, you'd find an ideal range of 138 to 172 bpm. If you're currently inactive, start out with lower goals: Multiply your HRR times just 40 and 50 percent and then add your RHR to both results to find your range.
Along with cardio, you also need strength training for peak physical health -- and there's no need to worry about heart rate with these exercises. For strengthening goodness, turn to free weights or weight machines, or use your body weight with squats, pushups and crunches. Two or three days per week, spend 20 to 30 minutes working every major muscle group: chest, back, arms, legs, stomach and buttocks. Give your muscles a break by waiting at least 24 hours between strength-training workouts.
- American Heart Association: Blood Pressure vs. Heart Rate
- MayoClinic.com: Exercise Intensity: Why it Matters, How it's Measured
- American Council on Exercise: Heart Rate Zone Calculator
- MayoClinic.com: Strength training: Get stronger, leaner, healthier
- Centers for Disease Control and Prevention: How Much Physical Activity do Adults Need?
- ACSM's Complete Guide to Fitness and Health; American College of Sports Medicine
- IDEA Health and Fitness Association
Nina K. is a Los Angeles-based journalist who has been published by USAToday.com, Fitday.com, Healthy Living Magazine, Organic Authority and numerous other print and web publications. She has a philosophy degree from the University of Colorado and a journalism certificate from UCLA.